Whether planets occur around other stars is fundamental both for the understanding of our own Solar System and for the issue of life in the Universe. Detecting planets is difficult because they are faint relative to their parent stars and their gravitational perturbations will typically be small and difficult to measure.
After years of conflicting claims, there seems to finally be emerging a body of observations supporting the existence of such extra-solar planets. Since most star systems are probably binary, this raises the additional question of whether there are planets in binary star systems.